XHHW and XHHW-2 wire in wet and feeder service

A thermoset wall instead of a thermoplastic one

XHHW is built as a compact or compressed stranded conductor under a wall of cross-linked polyethylene, sometimes with a nylon cover, sometimes bare. The insulation is cured rather than merely cooled, so it holds its shape under heat and resists the deformation that softens PVC. That is why the insulation wall is thinner than a comparably rated thermoplastic wire, and why the same conduit can carry more conductor.

The wet rating is the reason most of it is bought. XHHW is a wet-location conductor, permitted in underground raceways, exterior conduit and damp interior spaces. XHHW-2 extends that to 90°C in wet conditions where plain XHHW stops at 75°C wet. Both are often printed sunlight resistant. On a reel the string reads as size, then XHHW-2, then the voltage and the sunlight marking, and a reel printed XHHW alone will not carry the same ampacity in a wet run.

Aluminium XHHW in feeders

In mill and plant service, aluminium XHHW in 350 and 500 kcmil is ordinary. It is pulled from a substation or switchgear lineup to a remote MCC, run in conduit or tray, and landed on lugs listed for aluminium with antioxidant compound and a torque wrench. The conductor is AA-8000 series alloy, not the old utility-grade EC, and terminations are where these runs live or die.

That matters at resale. Aluminium feeder reels are often cut, not full: the last fifty feet of a run, coiled and taped, with the insulation stepped and the strands splayed from being pulled out of a lug. A buyer reading that lot wants to know whether the cut ends are square and capped and whether the reel was respooled or hand-coiled. Hand-coiled 500 kcmil is awkward freight, and it arrives with memory in it.

Water, reels and the storage question

Wet rated does not mean submersible. A reel standing in a puddle behind a Middletown plant takes water into the interstices between strands, and on aluminium that water sits there. The insulation is fine; the conductor ends are not. Reels stored flange-down in standing water are the ones that come in with white oxide bloom at the cut and a green cast on any exposed copper.

The other storage injury is mechanical. XHHW reels stacked on their side, or dragged across a yard, lose the outer wraps to the flange edge and to gravel. A scuffed jacket on the outer layer is a small loss on a full reel and a large one on a partial. Photographs of both flanges tell more than a description, because damage concentrates on the side that was down.

Reviewing a mill feeder lot

A plant disposing of feeder stock usually has it in three places: reels still on the rack, cut lengths on the floor under the rack, and a pile by the door that nobody has owned since the last outage. Those are three different lots and should be described separately rather than photographed together.

• Tag photographs for every full or near-full reel
• Cut lengths measured and listed by size, not estimated
• Conductor metal stated per reel, copper or aluminium
• Condition of the cut ends: capped, taped, oxidised or open
• Whether any reel has stood in water or lost outer wraps